Unfortunately Silverlight has let us down again. For one reason or another, the control doesn't export any images in the RichTextBox, or any other UIElement for that matter. It just returns an empty Run element instead.
Very frustrating!
Rather than shell out hundreds of pounds for third-party rich text box or use a unsupported free one such as the Liquid tools, we decided to write our out support manually.
To do this, we needed to manually export all of the RichTextBox contents, along with any InlineUIElements. Thankfully, there is a property on the RichTextBox which allows you to gain access to all the blocks within the control. From this you can iterate through them and with the help of reflection, write them all to a string builder. Fantastic!
The export function would like like this:
public string Export(RichTextBox rtb)
{
StringBuilder sb = new StringBuilder();
sb.Append("");
foreach (Block b in rtb.Blocks)
{
// Look at each block. They should either be a section or paragraph.
if (b is Paragraph)
{
Paragraph p = b as Paragraph;
writeElement(sb, p, false);
// Go through each inline within the paragraph
foreach (Inline i in p.Inlines)
{
if (i is InlineUIContainer)
{
// We need to look at these seperately as they have different requriements
InlineUIContainer inlineContainer = (InlineUIContainer)i;
parseInlineContainer(sb, inlineContainer);
}
else
{
// If its not an InlineUIContainer, our write element method will help!
writeElement(sb, i);
}
}
sb.Append("");
}
}
sb.Append(" ");
return sb.ToString();
}
Parsing the InlineUIContainer may look like this:
private void parseInlineContainer(StringBuilder sb, InlineUIContainer inlineContainer)
{
if (inlineContainer.Child is Image)
{
sb.Append("");
// If you want to be able to export other UIElements, this is where you handle them!
Image image = inlineContainer.Child as Image;
if (image.Source is BitmapImage)
{
BitmapImage bm = image.Source as BitmapImage;
string uri;
if (bm.UriSource.IsAbsoluteUri)
{
uri = bm.UriSource.AbsoluteUri;
}
else
{
uri = bm.UriSource.ToString();
}
sb.Append("![]()
");
}
sb.Append(" ");
}
}
And fleshing out the writeElement method may look something like this:
private void writeElement(StringBuilder sb, TextElement i, bool withClosingTag)
{
// Incase the control has any inlines (i.e. hyperlink)
InlineCollection inlines = null;
Type type = i.GetType();
sb.Append("<" + type.Name + " ");
foreach (PropertyInfo pi in type.GetProperties())
{
// Check if the property name is one of the ones we want
if (m_acceptableAttributes.Contains(pi.Name))
{
// Check if its readable and isn't null
if (pi.CanRead && pi.GetValue(i, null) != null)
{
// Get the value object and asset its something we're expecting
object valueObj = pi.GetValue(i, null);
if (valueObj is InlineCollection)
{
// Make sure we're not grabing inlines from a paragraph
if (i is Paragraph == false)
{
// If we have an inline collection, it means we have children, congrats!
inlines = valueObj as InlineCollection;
}
}
else
{
// Check if this element has inlines (hyperlink), if so we need to add them
string value = parsePropertyValue(i, valueObj);
// Append the property to the string builder
sb.Append(pi.Name + "=\"" + value + "\" ");
}
}
}
}
// Check if we have child inlines
if (inlines != null)
{
// Close of the control ready for children
sb.Append(" >");
foreach (Inline inline in inlines)
{
writeElement(sb, inline);
}
// Close the control
sb.Append("");
}
else
{
if (withClosingTag)
{
// If we need a closing tag, add one
sb.Append(" />");
}
else
{
// Otherwise just close the element
sb.Append(" >");
}
}
}
And finally the parsePropertyValue method could look like this:
private string parsePropertyValue(TextElement i, object valueObj)
{
string value;
if (valueObj is SolidColorBrush)
{
// If the value is a colour brush, use color value
SolidColorBrush brush = valueObj as SolidColorBrush;
value = brush.Color.ToString();
}
else if (valueObj is TextDecorationCollection)
{
// There is only every one text decoration for silverlight, underline.
// See remarks here: http://msdn.microsoft.com/en-us/library/ms603219(v=VS.95).aspx
value = "Underline";
}
else
{
value = valueObj.ToString();
}
return value;
}
So now we have the valid XAML, surely the RichTextBox should allow us to import the InlineUIElements within the XAML, using the XAML property... well, no.
It seems the control doesn't like importing InlineUIContainers as much as it likes exporting them. So we have to manually spoon feed the control again.
To do this, we used the XamlReader object, provided by the silverlight libraries, to load the XAML we manually exported into their respective instances. From this, we use the Blocks property on the control again to add each block one by one. Not so tricky
public void Import(RichTextBox rtb, string xaml)
{
// Load up the XAML using the XamlReader
Object o = XamlReader.Load(xaml);
if (o is Section)
{
// Make sure its a section and clear out the old stuff in the rtb
Section s = o as Section;
rtb.Blocks.Clear();
// Remove the blocks from the section first as adding them straight away
// to the rtb will throw an exception because they are a child of two controls.
List<Block> tempBlocks = new List<Block>();
foreach (Block block in s.Blocks)
{
tempBlocks.Add(block);
}
s.Blocks.Clear();
// Add them block by block to the RTB
foreach (Block block in tempBlocks)
{
rtb.Blocks.Add(block);
}
}
}
Eh voila! We have persisted a UIElement from the RichTextBox and loaded it back in again.
Of course, a solution like this would seem a bit nasty if we didn't have a nice neat export/import class which we could use, instead of the lack-luster XAML property, so thats what we've done!
You can download it below:
Source (49KB)
Binaries (8KB)
Feel free to use it any way you like!
Just to note, currently this library only exports InlineUIContainers which contain Images, but this could be easily extendible.
Also, the library isn't extensively tested, so please modify and use as you feel fit!
RichTextBox control for .NET
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